Pockels cells are one type of electro-optic (EO) device used to alter the polarization state of optical radiation. Pockels cells operate on a principle known as the Pockels or linear electro-optic effect, where an applied electric field produces linear changes in the refractive index of an optical material. This change in refractive index can be used to alter the phase of incoming light. The phase change can be used directly, or to alter the polarization state of incident light beams, with applications such as for Q-switching a laser.
Because their switching behaviour largely depends on the drive electronics which can deliver fast signals, Pockels cells generally provide a faster response time as compared to acousto-optic (AO) or liquid crystal based Q-switch devices. Non-linear optical (NLO) crystals are an example of a passive optical device that uses a related effect where the dielectric polarization responds nonlinearly to the electric E field of the light typically observed at high light intensities so that the values of the E field are comparable to interatomic electric fields in the NLO, typically 108 V/m such as those provided by lasers, allowing for frequency conversion (e.g., frequency doubling) by the NLO of an input laser pulse. In addition of these examples many other optical components would benefit from this advancement.
One of the most prevalent field failure modes for high-repetition rate and high-power optical devices, such as EO and NLO devices, is the degradation of the properties of the crystalline material due to thermal effects. The heat generated in the crystal from the applied electrical current and/or the absorption of laser light within the crystalline media or on the electrode facet due to a misaligned beam, can cause degraded optical device performance through thermal lensing, depolarization, and/or degradation of the electrical properties, while sometimes ultimately leading to the physical destruction of the crystalline material resulting from a significant reduction of the power handling capability.